NPM can't find local packages -- empty node_modules bin folder?

Ever had a situation where npm can't run local packages?

For example npm run tests is failing because the first thing it does is jest, and node can't find jest?

It could be that you haven't installed the packages, if so, use npm install to do that... but I think you know about npm install and it's probably not that.

What I found recently was that the folder node_modules/.bin was pretty much empty. What it should have had was a whole lot of files, three files for each command that can be run, e.g.

webpack
webpack.cmd
webpack.ps1

...and in a typical node_modules/.bin folder for a "real" project, there might be 160 files (for example). But in my project, it had only 3 such files...

How did this happen?

I'm not sure, but I suspect it was because I was urged to run a command & npm rebuild node-sass and murphy struck.

Generally if node_modules isn't behaving I run npm i (full name, npm install) and get things back in shape. In this case, it wasn't enough.

A good next step would've been:

• delete the package-lock file, and then
• run npm i

... i didn't do this, but suspect it would've helped.

The next fall back is: delete the entire node_modules folder, and then run npm i -- this was enough to help me in this case.